I'm trying to help a friend who has a Craftsman garage door opener
which just stopped working. According to him, I have not been to see it
yet,
the main controller in the garage and all the remotes do not work. The
main
controller is blinking a green light and the unit is humming. He said
the light on the unit turns on if he pushes the main controller light
button. Therefore, it's receiving power.

Broken or strippped belt ?